It has been known that halogen-containing organic polymers, especially the commerically important polyvinyl chloride polymers, are subject to deterioration or degradation when exposed to the deleterious effects of heat, light (especially ultra-violet light) and weathering. Various compounds and compositions have been proposed and utilized to stabilize these polymers against such degradation and deterioration. For the most part, these stabilizers have primarily been directed toward stabilization against the effects of heat, such as that encountered during processing of the polymer and fabrication thereof into articles. Among these primary heat stabilizers some of the most important and effective have been a wide variety of organotin compounds and non-tin metal salts.
Among the organotin compounds found to be effective heat stabilizers for halogen-containing polymers are organotin sulfides and mercaptides and organotin carboxylates and organotin mercaptocarboxylates. Among the non-tin metal salts found to be effective to stabilize said polymers there may be mentioned the antimony, barium, calcium, cadmium, zinc salts such as mercaptides, carboxylates and phenolates.
While these stabilizers have been quite effective as heat stabilizers for halogen-containing organic polymers they have generally only offered a modicum of light and weathering stabilization to the polymers. Yet, with the increasing use of halogen-containing organic polymers for rigid articles which will be exposed to light and outdoor weathering for extended periods of time, such as housing siding and window profiles, it has become increasingly important to develop a stabilizer which will not only protect the polymer against the high temperatures and heat encountered during processing and fabrication but will also protect the polymer against the extended and long-term effect of ultra-violet light and weathering as well.
It has also been known that plastic dispersions or pastes of vinyl chloride polymers or the like are plasticized by using as hydrophilic plasticizers, a hydriphilic fatty acid ester of a polyoxyalkylene glycol of a molecular weight of about 200 to 400 such as, for example, as disclosed in U.S. Pat. No. 3,957,712, issued May 18, 1976, to Heyden et al. Such hydrophilic plasticizers, when used in PVC plastic at plasticizing levels of 5 to 10% by weight, also impart antistatic properties and greater water vapor absorption properties. Similarly, U.S. Pat. No. 2,349,414, issued May 23, 1944, to Ferrer et al, discloses adding a plasticizing amount of from about 15 to 55% by weight of esters such as triethylene glycol di(2-ethylhexoate) and triethylene glycol di(2-ethylbutyrate) as plasticizers for colloidal dispersions of vinyl halide resins. The patentees state that organometallic compounds may be added to such compositions to increase the resistance of the plasticized plastic compositions to deterioration from light and heat.
In U.S. Pat. No. 3,479,308, issued Nov. 18, 1969 to Gattenby, Jr. et al, it is disclosed that by the addition of a combination of both (1) a partial ester of a water-soluble C.sub.2-6 polyol with a C.sub.12-18 aliphatic monocarboxylic acid and (2) a polyalkoxylated derivatives of a partial ester of a water soluble C.sub.2-6 polyol and a C.sub.12-18 aliphatic monocarboxylic acid, the alkoxylated groups each having between 2-3 carbon atoms and the number of alkoxy groups being 3-30 per molecule of the alkoxylated partial ester, to plasticized vinyl chloride films there is imparted antifogging and antitackifying properties to the films. The patentees state that conventional metal salt stabilizers may be added to the plasticized film.
U.S. Pat. No. 4,060,508, issued Nov. 29, 1977 to Sugahara et al, discloses that chlorine-containing polymers have a much reduced tendency to blow at the molding step if a silicate of a Group II and IV metal or composites of silicate acid with oxides, hydroxides and carbonates of said metals is employed along with organic additives having a boiling point or decomposition point higher than a chlorine-containing polymer processing temperature. Among the multitude of organic additives disclosed there is mentioned, at column 12, lines 13 and 14, a polyethylene glycol monofatty acid ester. The patent also mentions, at column 13, lines 6 to 9 and 37 to 49, that organic stablizers can also be added including organotin compounds and metal soaps.
In Japanese Patent Publication No. 59/164352, published Sept. 17, 1984, it is disclosed that glycols in combination with a mixture of more than 10% by weight of monoalkyltin tris (alkylthioglycolate) and less than 90% weight of dialkyltin bis (alkylthioglycolate) are employed as heat stabilizers for halogen-containing resins. The glycol compounds are added to the organotin heat stabilizers in order to eliminate or reduce the turbidity and subsequently produced precipitate resulting from a mixture of the dialkyltin bis (alkylthioglycolates) with the monoalkyltin tris (alkylthioglycolates).
However, satisfactory stabilization of halogen-containing polymers for rigid articles against degradation caused by exposure to light, especially UV light, and outdoor weathering for extended periods of time, has not yet been satisfactorily obtained and a great need exists for a stabilizer system that will protect against this form of degradation as well as the heat degradation encountered during polymer processing and fabrication.